1. Field of the Invention
The present invention relates to a platelike workpiece with an alignment mark to be used in an alignment apparatus for detecting an area to be processed or aligning attachment positions.
2. Description of the Related Art
In recent years, a mounting technique using Si through electrodes (Through-Silicon Via: TSV) instead of wires has received attention as a new three-dimensional mounting technique. For example, as a stacking method for semiconductor device chips, there has been developed a stacking method including the steps of stacking a plurality of semiconductor wafers and forming through electrodes extending through these stacked semiconductor wafers to thereby connect these stacked semiconductor wafers (Wafer On Wafer: WOW, see Japanese Patent Laid-open No. 2002-261232). In this stacking method, the upper and lower semiconductor wafers to be stacked are aligned in the following manner. Imaging means such as an infrared camera is used to image an alignment mark formed on the front side of the upper semiconductor wafer facing the imaging means and further image an alignment mark formed on the front side of the lower semiconductor wafer opposite to the imaging means as viewing through the upper semiconductor wafer. Thereafter, the alignment marks of the upper and lower semiconductor wafers are registered to thus perform an alignment operation.
Further, in the case of a semiconductor wafer having a plurality of circuits such as ICs and LSIs separated by a plurality of crossing streets, this semiconductor wafer is cut along the streets by using a cutting blade or a laser beam (dicing) to thereby obtain a plurality of individual semiconductor chips respectively including the circuits. In this manner, the dicing is performed along the streets. Accordingly, prior to performing the dicing, alignment is performed to detect the streets and align the cutting blade, for example, with each street at a cutting start position. This alignment is performed in the following manner. Imaging means in an alignment apparatus is used to image the front side of the semiconductor wafer. Thereafter, pattern matching is performed between an alignment mark formed on the front side of the semiconductor wafer and an alignment mark preliminarily stored in the alignment apparatus, thereby detecting the alignment mark on the front side of the semiconductor wafer. The detection of the alignment mark must be quickly performed in order to improve the productivity.